Pump casings are used to collect fluid induced by an impeller at an upstream location, and to channel this fluid to an outlet port located at a downstream location. Fluid flow path in pump casings are typically designed to convert dynamic energy (velocity) to pressure energy, i.e., to convert pump energy transmitted from the impeller to pressure energy.
Incorrectly sized and/or improperly manufactured casings may account for a significant portion of overall pump losses. Proper design of the fluid flow path in pump casings is critical to ensure overall pump performance and to minimize pump energy consumption. This is especially true for pumps used in MCSDs to assist the pumping action of the heart. Pump casings for MCSDs are generally volute-shaped with a cross-section of the volute (flow channel) increasing in a circumferential direction of the discharge in order to maintain a constant fluid velocity. The volute-shaped flow path is designed to maintain constant angular momentum (CAM) or a constant mean velocity (CMV).
Pump casings with intricate flow channels to achieve the desired flow characteristics have complex internal walls and do not easily lend themselves to fabrication by commonly used methods. Pump casings used in MCSDs are much smaller than pump casings used in most other applications in order to allow the MCSD to be implanted in a patient. The miniature scale of the MCSD pump casings further complicate the efforts to manufacture these pump casings by conventional methods. Pump casings of the size used in MCSDs are generally fabricated in two or more components which are attached to one another later. This further increases the effort of manufacturing these pump casings.